The hitherto-known moldable resin compositions having high strength and high elastic modulus include such resin-compositions as each comprises a polyol (e.g. a polyether polyol or a polyester polyol), an aromatic polyisocyanate (e.g. tolylene diisocyanate) and an aromatic polyamine (e.g. 3,3'-dichloro-4,4'-diaminodiphenylmethane), and such resin compositions as each comprises an NCO-terminated prepolymer derived from a polyol and an aromatic polyisocyanate, and an aromatic polyamine.
However, a shaped article obtainable by casting such a known resin composition into a casting mold and causing it to cure in situ is not satisfactory in mechanical properties such as hardness, strength and elastic modulus, and, moreover, is liable to vary its mechanical properties depending on temperature. Particularly at high temperatures exceeding about 80.degree. C., the characteristics of such shaped articles are considerably sacrificed. Therefore, these conventional resin compositions can hardly be employed for the manufacture of products required to be stable at high temperature. Furthermore, these resin systems are characterized by high reaction rates of components so that, on admixture of the components, the composition tends to undergo a sharp increase in viscosity or show a sudden evolution of intense heat. Therefore, these compositions are not only poor in storage stability and moldability but tend to cause troubles such as non-uniformity of products and cracking due to thermal shrinkage.
As a resin composition claimed to resolve the above-mentioned problems, Japanese Patent laid open No. 31420/1986 proposes a resin composition comprising an NCO-terminated urethane prepolymer derived from a polyol, an isocyanurate ring-containing polyisocyanate and a non-aromatic diisocyanate, and an aromatic polyamine. Japanese Patent laid open No. 1715/1989 also discloses a resin composition comprising an aromatic polyamine and an isocyanurate ring-containing aliphatic polyisocyanate.
The shaped articles obtainable from these resin compositions are somewhat superior to the earlier compositions in strength and modulus at high temperature but are not as satisfactory as desired in some or other quality parameters, namely hardness, strength, elastic modulus and elongation, as well as in toughness. Moreover, the temperature dependency of shaped articles are still large so that they suffer considerable losses in mechanical properties such as hardness, strength, elastic modulus and so on at high temperatures over 80.degree. C., particularly over 100.degree. C. The adhesiveness to certain adherends such as metal or plastic parts is not as high as desired, either. Therefore, in applications involving high temperatures where pressure hysteresis is inevitable, the durability of shaped articles is sacrificed to considerably limit their utility range.